1. Field of the Invention
The present invention relates to a fuel cell including a plurality of power generation cells each formed by stacking an electrolyte electrode assembly and a separator together in a stacking direction. The electrolyte electrode assembly includes a pair of electrodes and an electrolyte interposed between the electrodes. A reactant gas flow field for supplying a fuel gas or an oxygen-containing gas as a reactant gas along one electrode is formed on one surface of the separator facing the one electrode, and a reactant gas supply passage extends through at least one corner of the power generation cell in the stacking direction for allowing the reactant gas to flow through the reactant gas passage and flow into the reactant gas flow field.
2. Description of the Related Art
For example, a solid polymer electrolyte fuel cell employs a membrane electrode assembly (MEA) which includes an anode, a cathode, and an electrolyte membrane interposed between the anode and the cathode. The electrolyte membrane is a polymer ion exchange membrane. The membrane electrode assembly and a pair of separators sandwiching the membrane electrode assembly make up a power generation cell. In use, generally, a predetermined number of power generation cells of this type are stacked together to form a fuel cell stack mounted in a vehicle.
In the fuel cell, a fuel gas flow field (reactant gas flow field) is formed in a surface of one separator facing the anode for supplying a fuel gas (reactant gas) to the anode, and an oxygen-containing gas flow field (reactant gas flow field) is formed in a surface of the other separator facing the cathode for supplying an oxygen-containing gas (reactant gas) to the cathode. Further, a coolant flow field is formed between adjacent separators for supplying a coolant along surfaces of the separators.
Further, in many cases, the fuel cell of this type adopts a so-called internal manifold structure where in the interior of the fuel cell, there are provided a fuel gas supply passage (reactant gas supply passage) and a fuel gas discharge passage (reactant gas discharge passage) through which the fuel gas flows, an oxygen-containing gas supply passage (reactant gas supply passage) and an oxygen-containing gas discharge passage (reactant gas discharge passage) through which the oxygen-containing gas flows, and a coolant supply passage and a coolant discharge passage through which the coolant flows, each of which extends through the fuel cell in the stacking direction of the power generation cells.
For example, as a fuel gas having the internal manifold structure, a fuel cell having a separator structure disclosed in Japanese Laid-Open Patent Publication No. 2008-021515 is known. As shown in FIG. 7, the separator structure comprises a metal plate 1, and an oxygen-containing gas manifold 2, a coolant manifold 3 and a fuel gas manifold 4 extend through an end portion of the metal plate 1.
A fuel gas flow field 5 is formed in a surface of the metal plate 1, and a fuel gas distribution area 6 and a fuel gas inlet 7 are provided between the fuel gas flow field 5 and the fuel gas manifold 4. A plurality of bosses 6a are provided in the fuel gas distribution area 6. The fuel gas inlet 7 has a plurality of inlet grooves 7a adjacent to the fuel gas manifold 4.
In the structure, the fuel gas supplied through the fuel gas manifold 4 to the metal plate 1 flows into the fuel gas distribution area 6 through the inlet grooves 7a, and thereafter the fuel gas is supplied to the fuel gas flow field 5.
However, in Japanese Laid-Open Patent Publication No. 2008-021515, the fuel gas manifold 4 is provided at the one corner of the metal plate 1. The fuel gas introduced into the fuel gas inlet 7 through the fuel gas manifold 4 is difficult to supply uniformly over the entire fuel gas flow field 5.
In particular, the fuel gas is not supplied sufficiently to an area 8 which is remote from the fuel gas inlet 7. In this area 8, power generation cannot be performed suitably.